/Engine/Source/Runtime/UMG/Public/Components/ListViewBase.h
UListView::OnRefreshDesignerItemsfor a usage example
template<typename PlaceholderItemT> void RefreshDesignerItems ( [TArray](API\Runtime\Core\Containers\TArray)< PlaceholderItemT > & ListItems, [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< PlaceholderItemT()> CreateItemFunc )